Doctor's Notes on Psoriasis
Psoriasis is a chronic autoimmune skin disorder that causes patchy, red, scaly areas of skin. It typically affects the arms, legs, trunk, scalp, knees, elbows, and lower back but it may occur on any part of the skin. The most common form of psoriasis is called plaque psoriasis (psoriasis vulgaris).
Symptoms of plaque psoriasis include plaques that are red, raised, scaly skin affecting the scalp, elbows, and knees. The plaques may itch or burn. Flares (periods when the condition worsens) may last weeks to months. Plaques may split and bleed, especially when they occur over joints or on the palms or feet. Plaques may be surrounded by a halo or ring of blanched skin (Ring of Woronoff). Skin scales are silvery white and thickness varies. Other symptoms of psoriasis include nail changes such as discoloration and separation from the nail bed at the fingertip. In children, symptoms of plaque psoriasis may appear different. Plaques are not as thick and the affected skin is less scaly. Psoriasis often appears in the diaper region in infancy and in flexural areas (underarms, groin, perianal area) and the face in children.
Plaque psoriasis (psoriasis vulgaris), the most common form, usually produces plaques of red, raised, scaly skin affecting the scalp, elbows, and knees. The plaques may itch or burn.
The flare-ups can last for weeks or months. Psoriasis can spontaneously resolve only to return later.
- Plaques: They vary in size (1 centimeter to several centimeters) and may be stable for long periods of time. The shape of the plaque is usually round with irregular borders. Smaller plaques may merge, producing extensive areas of involvement.
The skin in these areas, especially when over joints or on the palms or feet, can split and bleed.
Plaques sometimes may be surrounded by a halo or ring of blanched skin (Ring of Woronoff). This is especially noticeable after effective treatment has begun and the lesions are resolving.
- Red color: The color of the affected skin reflects the inflammation present and is caused by increased blood flow.
- Scale: The scales are silvery white. The thickness of the scales may vary. When the scale is removed, the skin underneath looks smooth, red, and glossy. This shiny skin usually has small areas of pinpoint bleeding (Auspitz sign).
- Symmetry: Psoriatic plaques tend to appear symmetrically on both sides of the body. For example, psoriasis is usually present on both knees or both elbows.
- Nails: Nail changes are common in psoriasis. The nails may have small indentations or pits. The nails can be discolored and separate from the nail bed at the fingertip. (See Nail Psoriasis.) This may be similar in appearance to fungal nail infections and may actually coexist with, a fungal infection.
- Psoriasis in children: Plaque psoriasis may look slightly different in children. In children, the plaques are not as thick, and the affected skin is less scaly. Psoriasis may often appear in the diaper region in infancy and in flexural areas in children. The disease more commonly affects the face in children as compared to adults.
- Other areas: Although the most common body areas affected are the arms, legs, back, and scalp, psoriasis can be found on any body part. Inverse psoriasis can be found on the genitals or buttocks, under the breasts, or under the arms and may not show the scale typically seen in other body areas. These areas can feel especially itchy or have a burning sensation.
Research indicates that the disease results from a disorder in the inflammatory system. In psoriasis, T lymphocytes (a type of white blood cell) abnormally trigger inflammation in the body. These T cells also stimulate skin cells to grow faster than normal and to pile up in raised plaques on the outer surface of the skin.
Those with a family history of psoriasis have an increased chance of having the disease. Some people carry genes that make them more likely to develop psoriasis. When both parents have psoriasis, their offspring have a 50% chance of developing psoriasis. About one-third of those with psoriasis can recall at least one family member with the disease.
Certain risk factors may trigger a psoriasis flare.
- Injury to the skin: Injury to the skin has been associated with plaque psoriasis. For example, a skin infection, skin inflammation, or even excessive scratching can trigger psoriasis at the site of the skin injury.
- Sunlight: Most people generally consider sunlight to be beneficial for their psoriasis and therapeutic phototherapy is a treatment option. However, a small minority find that strong sunlight aggravates their condition. A bad sunburn may worsen psoriasis.
- Streptococcal infections: Streptococcal sore throats may trigger guttate psoriasis, a type of psoriasis that looks like small red drops on the skin.
- HIV: Psoriasis may worsen after an individual has been infected with HIV.
- Drugs: A number of medications have been shown to aggravate psoriasis. Some examples are as follows:
- Lithium: Drug that may be used to treat bipolar disorder
- Beta-blockers: Drugs that may be used to treat high blood pressure
- Antimalarials: Drugs used to treat malaria, arthritis, and lupus
- NSAIDs: Drugs, such as ibuprofen (Motrin and Advil) or naproxen (Aleve), used to reduce inflammation
- Emotional stress: Many people note worsening of their psoriasis when emotionally stressed.
- Smoking: Cigarette smokers have an increased risk of chronic plaque psoriasis because smoking may alter the immune system in such a way as to cause a flare of the condition.
- Alcohol: Alcohol is considered a risk factor for psoriasis. Even moderate intake of beer may trigger or worsen psoriasis.
- Hormonal changes: The severity of psoriasis may fluctuate with hormonal changes. Disease frequency peaks during puberty and menopause. During pregnancy, psoriatic symptoms are more likely to improve. In contrast, flares occur in the postpartum period.
Psoriasis is a genetically programmed inflammatory disease that primarily affects the skin in about 3% of individuals in the United States. Psoriasis is characterized by skin cells that multiply up to 10 times faster than normal. When these cells reach the surface and die, raised, red plaques covered with white scales form. Psoriasis begins as a small scaling papule. When multiple papules coalesce, they form scaling plaques. These plaques tend to occur in the scalp, elbows, and knees.
Psoriasis : Test Your Medical IQ QuizQuestion
Psoriasis causes the top layer of skin cells to become inflamed and grow too quickly and flake off.See Answer
Kasper, D.L., et al., eds. Harrison's Principles of Internal Medicine, 19th Ed. United States: McGraw-Hill Education, 2015.